Hard disk drives such as the exemplary drive 10 illustrated in FIG. 1a include one or a stack of magnetically coated platters 12 that are used for storing information. The magnetically coated platters 12 are mounted together in a stacked position through a spindle 14 which may be referred to as a platter stack. The platter stack is typically rotated by a motor that is referred to as a spindle motor or a servo motor (not shown). A space is provided between each platter to allow an arm 18 having a read/write head or slider 20 associated therewith to be positioned on one or both sides of each platter 12 so that information may be stored and retrieved. Information is stored on one or both sides of each platter 12 and is generally organized into sectors, tracks, zones, and cylinders.
Each of the read/write heads or sliders 20 are mounted to one end of the dedicated suspension arm 18 so that each of the read/write heads may be positioned as desired. The opposite end of each of the suspension arms 18 are coupled together at a voice coil motor 16 (VCM) to form one unit or assembly (often referred to as a head stack assembly) that is positionable by the voice coil motor. Each of the suspension arms 18 are provided in a fixed position relative to each other. The voice coil motor 16 positions all the suspension arms 18 so that the active read/write head 20 is properly positioned for reading or writing information. The read/write heads 20 may move from at least an inner diameter to an outer diameter of each platter 12 where data is stored. This distance may be referred to as a data stroke.
Hard disk drives also include a variety of electronic circuitry 30 for processing data and for controlling its overall operation as illustrated in FIG. 1b. This electronic circuitry 30 may include a pre-amplifier 32, a read channel/write channel circuit 33, a servo controller 34, a motor control circuit 35, a read-only memory 36 (ROM), a random-access memory 37 (RAM), and a variety of disk control circuitry such as an HDD controller 38 or microprocessor to control the operation of the hard disk drive and to properly interface the hard disk drive to a system bus 39, and voltage regulators to supply voltages needed other than the ones from the power plug. The pre-amplifier 32 may contain a read pre-amplifier and a write pre-amplifier that is also referred to as a write driver. The pre-amplifier 32 may be implemented in a single integrated circuit or in separate integrated circuits such as a read pre-amplifier and a write pre-amplifier or write driver. The disk control circuitry 38 generally includes a separate microprocessor for executing instructions stored in memory to control the operation and interface of the hard disk drive.
Hard disk drives perform write, read, and servo operations when storing and retrieving data. The preamplifier circuit IC is located proximate to the arms 18 and a flex 50 is used to couple the signals back and forth to the remaining circuitry on a printed circuit board (PCB) 52 (see e.g., FIG. 2b). The PCB 52 contains the remaining circuitry of FIG. 1b and receives power from a power plug into a receptacle. An exemplary plan view of a plug receptacle or socket is illustrated in FIG. 2c, and designated at reference numeral 54. The non-portable PC industry standard socket 54 will comprise a four pin male type connector for providing supply voltage potentials of 5V, GND, GND and 12V, respectively, to the PCB circuitry.
The non-portable PC industry standard socket 54 further includes two 45 degree filled corner tabs 56 which serve as a key to discourage plugging a power plug into the socket 54 in the wrong way, for example, reversing the plug. Unfortunately, in some cases it is still possible to force the power plug into the socket 54 in an improper orientation if sufficient force is exerted on the power plug. In such cases, the 5V and 12V supply voltages are switched, and circuitry intended to receive 5V may receive 12V, which may result in an electrical overvoltage stress (EOS) related circuit failure.
The 5V only or 3.3V only (no 12V) HDDs for portable PCs use a different power plug configuration. In the non-portable use, a 5V HDD with a different plug configuration may use a socket adapter to the non-portable industry standard socket 54, and there the possibility of reverse plugging the socket adapter still exists.
In addition, the circuitry on the PCB 52 is powered by system power supplies not located thereon which may not be adequately regulated or, in some cases, may be defective. Such system conditions may result in overvoltage conditions at either or both of the 5V and 12V pins, respectively, even when the power plug is properly inserted into the socket 54. Such overvoltage conditions may also contribute to EOS related circuit failures.